Friday, January 3, 2025
1/3/2025
PROJECT ABSTRACT: Osteosarcoma (OS) is the most common primary bone malignancy worldwide and primarily affects adolescents. While the 5-year survival rate is around 70% with localized disease, metastatic disease survival remains a dismal 20% with little improvement over past years. It is recognized that interactions within the microenvironment can either facilitate or inhibit cancer cell metastasis, thus a deeper analysis of these interactions may identify targetable vulnerabilities of metastatic OS. Previous studies by our lab and others have shown that platelets promote metastasis of several types of cancer. In contrast, the role of megakaryocytes (MKs), platelet producing cells, in cancer metastasis has not been established. While MKs are primarily recognized as platelet producers, they also serve as dynamic regulators of bone production that both influence and are influenced by bone cells. A previous study found that co-culture of OS cells with MKs increased OS proliferation suggesting that MKs could influence OS cells within the bone microenvironment Additionally, a study found that breast cancer tumor bearing mice displayed altered MK polyploidy and increased platelet RNA and protein content demonstrating that tumors can influence MK function and alter the produced platelets. My preliminary data suggests that platelet depletion in mice decreases initial lung seeding of OS cells administered via tail vein. My preliminary data also shows increased MKs but decreased MK ploidy in mice with orthotopic OS tumors. Based on these previous studies and my preliminary data, I hypothesize that OS and MK bidirectional signaling contributes to OS progression and metastasis by exchanging signaling mediators that lead to alterations in MK differentiation, maturation, platelet production and function, while also increasing OS cell proliferation and migration in the primary tumor. To study this mechanism, I will use a novel tibial implantation technique to establish orthotopic primary tumors in both wild-type and MK-depletion mice (PF4CreiDTR mice). I will use this approach to test the following specific aims: Aim 1 is to test the hypothesis that OS primary tumors dysregulate MK differentiation and maturation leading to altered platelet proteome content. and function. I will perform the tibial implant procedure or a sham procedure on WT mice and compare bone marrow MK maturation and differentiation via flow cytometry across three time points to evaluate changes in MKs throughout OS tumor progression. I will assess platelet function and activation from both groups via aggregometry and flow cytometry. Finally changes in MK transcriptome and platelet proteome will be compared between groups. Aim 2 is to test the hypothesis that MK-OS interactions during primary OS tumor development promote OS cell proliferation and metastasis. I will deplete MKs in OS tumor bearing mice and examine how tumor growth, proliferation, lung metastasis, and the tumor transcriptome compare to wild-type (WT) mice. The results of these experiments will reveal how OS-MK interactions affect OS metastasis and identify candidate mediators for future study of the mechanisms involved and of their potential as therapeutic targets.
HHS’ Tracking Accountability in Government Grants System (TAGGS) website provides access to detailed descriptions of grants, loans, aggregated direct payments and other types of financial assistance awarded by the HHS Operating Divisions (OPDIVs) and the Office of the Secretary Staff Divisions (STAFFDIVs).